1. Field of the Invention
The present invention relates to a photosemiconductor module capable of emitting light or detecting the intensity of received light, for use in optical communications.
2. Description of the Prior Art
Photosemiconductor modules are used to obtain a predetermined coupled condition between a photosemiconductor and an optical fiber for achieving a desired intensity of light transmitted between the photosemiconductor and the optical fiber. Generally, the photosemiconductor modules include a lens to be disposed between the photosemiconductor and the optical fiber to adjust the coupled condition.
One conventional photosemiconductor module is shown in FIG. 6 of the accompanying drawings. The photosemiconductor module includes a photosemiconductor 100 and a lens 101 which are fixed in position by an adhesive or the like in an integral holder 102 made of brass or the like. The holder 102 is joined by a solder 104 or laser welding to an optical connector 103 which includes a receptacle of brass or the like that is to be connected to a plug (not shown) coupled to an optical fiber.
Another known photosemiconductor module includes separate holders for a photosemiconductor and a lens, as disclosed in Japanese Laid-Open Utility Model Publication No. 63(1988)-128748, for example.
The photosemiconductor modules are however incapable of adjusting the lens along an optical axis thereof (i.e., in the direction of the Z-axis). Therefore, elaborate and detailed design configurations are necessary to fix the photosemiconductor and the lens to the holder or holders since the photosemiconductor and the lens cannot be relatively adjusted in position along the optical axis while the optically coupled condition is being monitored when these photosemiconductors are assembled.
The optical connector 103 shown in FIG. 6 is of a unitary structure. In order to join the holder 102 and the optical connector 103 to each other by the solder 104 or laser beam welding, the optical connector 103 has to be machined highly accurately from a mass of hard metal which is not easy to cut.
The holder 102 and the optical connector 103 are held in abutment against each other. When the holder 102 and the optical connector 103 are welded to each other by a laser beam, it is required to slightly adjust the position where the laser beam is applied radially to the joint between the holder 102 and the optical connector 103, because the area in which the holder 102 and the optical connector 103 are welded together tends to vary depending on the position where the laser beam is applied. Consequently, the photosemiconductor modules cannot be assembled efficiently at a high production rate. The qualities, such as mechanical strength and distortion, of the photosemiconductor module reflect the condition in which the laser beam is applied.
The region where the holder 102 and the optical connector 103 is joined together is exposed to the exterior. Therefore, the joined region has poor environmental resistance against heat cycles, humidity, and other environmental factors. If the photosemiconductor and the lens are held in different holders, respectively, relative positional adjustments of the holders in directions normal to the optical axis (i.e., the directions of the x- and y-axes) result in irregularities in the outer profile of the photosemiconductor module. The outer profile of the photosemiconductor module is thus liable to have a poor coaxial configuration.
In the cases where the components of the photosemiconductor are assembled and secured together by adhesive bonding or soldering, the optical axis of the module will be slightly deflected in a heat-cycle load test or the like. Then, the photosemiconductor module cannot produce a stable optical output if the plug is connected to a single-mode fiber rather than a multimode fiber, and hence is not reliable enough in operation. The adhesive bonding process allows the components to be positionally displaced when the adhesive is heated and hardened, and also requires a certain period of time to elapse until the components are completely joined together. Accordingly, the assembling procedure is composed of an increased number of steps and is time-consuming. In addition, although the photosemiconductor module is relatively simple in construction, it cannot automatically be assembled because of the adhesive bonding process required.